7 mars, 2011

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Triode

We frequently get the question why our speakers are active and why we are not using a triode amplifier.

Valid question as horns are efficient requiring low average power. From this standpoint tubes would do fine. Certainly this was tried during the design phase of the Earo Eight. in fact we tried out a lot of different amplifiers types. We did blind A-B tests between silicon and tube classes. Our own tube amps is a pair of modernised Quad II´s. We could easily drive them to 95+dB levels at the listening position with the 12watts or so delivered from this Class A output.

Because the Earo designs offer such high degree of detail in the reproduction, asessing performance of the entire playback chain is revealing. We found that the audiophile D-Class designs used in all Earo speakers gave an overall better result.

One explanation for this is that tubes are high impedance devices and loudspeaker drivers are low impedance why the fundamental mismatch requires an electrical transformer. Unfortunately this transformer does not offer the milli-ohm range output impedance that D-Class can do. Low source impedance is particularly important to optimize the driver performance for horns.

Another added benefit is that whilst D-Class can produce amazing low THD figures and being independent over the frequency range, they tend to be particularly low in THD in a power range around 1/10 of rated power. Exactly where Earo speakers takes out its average power. This also adds the beneficial consequence of having a large power margin giving flawless impulse response capability.

This and more is found in the White paper ”nearly a complete case for the horn” found on the website www.earo.eu